On 10/23/2013 06:58 PM, Thierry Reding wrote: > On Wed, Oct 23, 2013 at 06:46:17PM +0800, Mark Zhang wrote: >> On 10/23/2013 06:36 PM, Mark Zhang wrote: >>> On 10/23/2013 05:09 PM, Thierry Reding wrote: >>>> On Wed, Oct 23, 2013 at 04:49:29PM +0800, Mark Zhang wrote: >>>>> On 10/23/2013 04:00 PM, Thierry Reding wrote: >>>>>> On Wed, Oct 23, 2013 at 10:16:24AM +0800, Mark Zhang wrote: >>>>>>> On 10/22/2013 08:49 PM, Thierry Reding wrote: >>>>>>>> On Tue, Oct 22, 2013 at 04:55:09PM +0800, Mark Zhang wrote: >>>>>>>>> On 10/22/2013 03:24 PM, Thierry Reding wrote: >>>>>>>>>> On Fri, Oct 18, 2013 at 12:48:12PM +0800, Mark Zhang wrote: >>>>>>>>> [...] >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Okay, I just want to set the "notify" function pointer in "struct >>>>>>>>>>> platform_pwm_backlight_data", because I want to tune the brightness >>>>>>>>>>> value before the pwm-bl sets the brightness to hardware. I don't know >>>>>>>>>>> how to do that, unless we define the platform data explicitly. >>>>>>>>>> >>>>>>>>>> Okay, my question should have been what you need the functions for and >>>>>>>>>> why you think you need them. >>>>>>>>>> >>>>>>>>> >>>>>>>>> If I understanding you correctly, I suppose I've said that: "because I >>>>>>>>> want to tune the brightness value before the pwm-bl sets the brightness >>>>>>>>> to hardware". >>>>>>>> >>>>>>>> Why do you want to tune the brightness value? What are you trying to >>>>>>>> achieve? >>>>>>>> >>>>>>> >>>>>>> Oh, Tegra has a feature named PRISM(aka SmartDimmer). It changes the >>>>>>> color value to make the display looks bright so that we can reduce the >>>>>>> backlight brightness to save power. So everytime PRISM is triggered, we >>>>>>> call "backlight_update_status", then in the "notify" callback, we change >>>>>>> the brightness value which pwm-bl provides by considering the PRISM >>>>>>> compensations. >>>>>> >>>>>> If you automatically call backlight_update_status() everytime PRISM >>>>>> gives you new data, can't you just pass the correct value in in the >>>>>> first place so that you don't have to tweak it in the .notify() >>>>>> callback? >>>>> >>>>> OK, how to do that? -- "pass the correct value in in the first place"? >>>> >>>> Well, if you call backlight_update_status(), then you can pass in a >>>> brightness value, right? You usually do that by setting the backlight's >>>> props.brightness field. >>>> >>>> So when PRISM gives you new data, you could just read out the current >>>> brightness, compute the new one based on the current one and the PRISM >>>> data, set the props.brightness field to that value and then call >>>> backlight_update_status(). >>>> >>> >>> Okay, anyway, I got the idea. Actually it's simpler. :) >>> I'm just curious that if we can do that in this way, why we need >>> "notify" anymore? >> >> Oh, by the way, how about "check_fb" fops? Is there some kind of >> substitution as well? I mean, if I wanna set "check_fb" and also want to >> define the backlight device via DT, is there a way to do that? > > No, there's no substitution for that. .check_fb() is used to verify that > a backlight device is associated with a framebuffer device. There are > better ways to check for that with DT, although nothing has been merged > into mainline yet. > Okay, thanks for the explanation. Mark > Thierry > -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html